Two Dutch F-16s based in the southern Afghan city of Kandahar were called in to provide air support to soldiers from NATO's International Security Assistance Force (ISAF) engaged in intense combat with insurgents fighting from a compound in Nad Ali district of troubled Helmand province on Wednesday.

Only one of the warplanes dropped a bomb, said Visser.

"All of the procedures to pinpoint combatants were respected," she said. "If there had the smallest doubt regarding the presence of civilians they wouldn't have acted."

According to Helmand region officials, six children and three women were killed in the attack, with at least three other civilians injured.

"That's terrible, it is something we never wanted to see happen and we try at all costs to avoid," said Visser.

Civilian casualties are a sensitive issue in Afghanistan, creating a rift between President Hamid Karzai's government and international forces as well as resentment on the ground against foreign troops.

Some 100,000 NATO and US-led troops are stationed in Afghanistan, helping the government fight a Taliban insurgency that is at its most deadly since the 2001 US-led invasion toppled the hardline regime.